The applicant's patent application DE 199 12 480 A1 describes an automatically shiftable motor vehicle transmission having three single-carrier planetary gear sets, three brakes and two clutches for the shifting of six forward gear ratios and one reverse gear ratio, and having a drive shaft and an output shaft. The drive shaft is connected directly to the sun gear of the second planetary gear set, and is connectable by the first clutch to the sun gear of the first planetary gear set and by the second clutch to the carrier of the first planetary gear set. The sun gear of the first planetary gear set is connectable by the first brake, the carrier of the first planetary gear set is connectable by the second brake, and the sun gear of the third planetary gear set is connectable by the third brake, to the housing. The carrier of the first planetary gear set is connected to the ring gear of the second planetary gear set. The carrier of the second planetary gear set is connected to the ring gear of the third planetary gear set. The ring gear of the first planetary gear set is connected to the carrier of the third planetary gear set and to the output shaft. Furthermore, freewheels may be used at every point of the transmission, for example between a shaft and the housing.
The patent U.S. Pat. No. 8,858,376 B2 describes a transmission for a hybrid drivetrain of a vehicle, which exhibits substantially the same construction. Furthermore, said transmission includes an electric machine which is connected to the input shaft. By a launch clutch, the input shaft is connected via a damper to a motor. A freewheel connects the second element of the first planetary gear set to the housing.
The applicant's patent application DE 103 33 429 A1 presents an arrangement of the brakes and clutches for the motor vehicle transmission known in the prior art, wherein the second brake, designated D, and the first brake, designated C, are arranged directly adjacent to the first planetary gear set. Here, the second brake is arranged radially outside the first brake. Both brakes are formed as multiplate brakes.
Transmissions for hybrid vehicles commonly have an increased structural space requirement owing to the electric machine. Depending on the arrangement of the drivetrain, that is to say either parallel or transverse to the direction of travel of the hybrid vehicle, this has different effects on the hybrid vehicle. In the case of a drivetrain parallel to the direction of travel, the space availability in the interior compartment of the hybrid vehicle is impaired by the increased axial structural length. This is undesirable. In the case of a drivetrain transverse to the direction of travel, the structural space is greatly limited, because the assembly composed of internal combustion engine, electric machine and transmission is normally arranged between the longitudinal members and the wheels of the hybrid vehicle.
Furthermore, in a drivetrain, good mechanical efficiency must always be ensured. Frictionally locking shift elements, such as for example multiplate brakes, impair the efficiency, because they generate drag losses in the open state. In the case of the motor vehicle transmission known in the prior art, such drag losses arise to a particularly great extent at the second brake, because said second brake must be designed with a particularly large effective surface owing to the high torque loading, and because said second brake is closed only in the first forward gear ratio and in the reverse gear ratio. The second brake is therefore predominantly open during the operation of the motor vehicle transmission. Frictionally locking shift elements however improve the powershift characteristics of the motor vehicle transmission, and thus the shift comfort for the driver of the motor vehicle.